What is the best antibiotic for a sinus infection?

Best Antibiotic for Sinus Infection

Amoxicillin-clavulanate is the preferred first-line antibiotic for acute bacterial sinusitis in adults, dosed at standard strength (875 mg/125 mg twice daily) for 7-10 days. 1, 2

First-Line Treatment Selection

The choice of antibiotic depends on infection severity and patient risk factors:

Standard First-Line Therapy

• Amoxicillin-clavulanate (875 mg/125 mg twice daily) is recommended as the primary choice due to increasing prevalence of beta-lactamase-producing organisms like H. influenzae and M. catarrhalis 3
• Plain amoxicillin (500 mg twice daily for mild infections, 875 mg twice daily for more severe) remains acceptable for uncomplicated cases in patients without recent antibiotic exposure 1
• Duration: 7-10 days until symptom-free for 7 days 1, 4

Alternative First-Line Options (Penicillin Allergy)

For patients with penicillin allergy, use second or third-generation cephalosporins 1, 2:

• Cefuroxime-axetil
• Cefpodoxime-proxetil
• Cefdinir
• Pristinamycin (specifically for beta-lactam allergy) 4, 1

Important caveat: Some cephalosporins (cefuroxime-axetil, cefpodoxime-proxetil) have demonstrated effectiveness in shorter 5-day courses 4, 2

Treatment Based on Sinusitis Location

The anatomic site of infection determines antibiotic selection and urgency 4:

Maxillary Sinusitis (Most Common)

• Standard first-line antibiotics as above 4, 1
• Clinical features: unilateral/bilateral infraorbital pain worsening when bending forward, purulent discharge 4

Frontal, Ethmoidal, or Sphenoidal Sinusitis (Higher Risk)

• Reserve fluoroquinolones (levofloxacin 500-750 mg daily or moxifloxacin 400 mg daily) for these locations due to higher complication risk 4, 1
• These sites require more aggressive treatment given proximity to critical structures 4
• Fluoroquinolones should also be reserved for treatment failure of maxillary sinusitis 4, 1

Second-Line Treatment for Treatment Failure

If no improvement occurs within 3-5 days 1, 2:

• Switch to high-dose amoxicillin-clavulanate (if not already used) 1, 2
• Consider respiratory fluoroquinolones (levofloxacin 750 mg daily for 5 days or 500 mg daily for 10 days; moxifloxacin 400 mg daily for 10 days) 4, 1, 5, 6
• Obtain bacteriological and/or radiological investigations before escalating to fluoroquinolones 4

Critical note: A 2021 randomized trial found that high-dose amoxicillin-clavulanate (double amoxicillin component) provided no additional benefit over standard dosing in adults with acute sinusitis, though diarrhea rates were similar 7. This challenges older recommendations for dose escalation.

Adjunctive Therapies

Beyond antibiotics, consider 1, 2:

• Intranasal corticosteroids as adjunct to antibiotic therapy 1, 2
• Short-term oral corticosteroids for acute hyperalgic sinusitis (severe pain) or marked mucosal edema 4, 1
• Adequate hydration, analgesics, warm facial packs, sleeping with head elevated 1
• Short-term decongestants (topical <3 days to avoid rhinitis medicamentosa) 3

Common Pitfalls to Avoid

• Don't use antibiotics for viral rhinosinusitis: Only prescribe when bacterial sinusitis is clinically established (symptoms >10 days without improvement, severe symptoms with high fever and purulent discharge for 3-4 days, or worsening after initial improvement) 3, 8
• Don't reserve fluoroquinolones for simple maxillary sinusitis: These should be saved for complicated cases, treatment failures, or high-risk anatomic locations 4, 1
• Don't stop antibiotics early: Complete the full 7-10 day course even after symptom improvement to prevent relapse 1
• Watch for complications: Facial swelling, visual changes, severe headache, or meningeal signs require immediate evaluation and possible hospitalization 4

Special Populations

Pediatric Considerations

• Amoxicillin 45 mg/kg/day (standard) or 80-90 mg/kg/day (high-dose for resistant S. pneumoniae) in 2 divided doses 4, 1
• Amoxicillin-clavulanate 80-90 mg/kg/day (amoxicillin component) for children <2 years, in daycare, or with recent antibiotic use 4, 1
• Single-dose ceftriaxone 50 mg/kg for children unable to tolerate oral medication 4, 1

Recurrent Sinusitis

Evaluate for underlying factors: allergic rhinitis, immunodeficiency, anatomic abnormalities; consider referral to allergist-immunologist or otolaryngologist 1, 2